Abstract:

The kinematic characteristics and thermophoretic deposition of inhalable particles（PM2.5）suspended in air flow in a vertical rectangular duct with temperature distribution were experimentally studied.Particle dynamics analyzer（PDA）was used for the on-line measurement of particle motion and particle concentration distribution in the cross-sections of the duct.Influence of the parameters such as the ratio of the bulk air temperature to the cold wall temperature in the duct on the kinematic characteristics and the deposition efficiencies of PM2.5 was investigated.Experimental results indicate that the particle concentration distribution in the duct，extremely in the area near the walls，is mainly determined by the turbulent diffusion in the flow，but turbulent diffusion is hard to make particles to deposit on the dust walls. Thermophoresis is the key factor to the particle deposition on the cold duct walls.Based on the experimental results，an empirical correlation for the calculation of thermophoretic deposition efficiency of PM2.5 is developed.The empirical correlation agrees reasonably well with the experimental data.

Key words: 可吸入颗粒物, 热泳力, 沉积效率

摘要：

对温度梯度场内垂直管中可吸入颗粒物在湍流工况下的运动特性和热泳沉积规律进行了实验研究，使用颗粒动态分析仪（PDA）在线测量了颗粒物在管道截面上的速度和浓度分布。重点研究了主流与水冷壁面的温差对粒径范围0～2.5 μm颗粒（PM2.5）的运动和沉积的影响，得到其沉积效率。结果表明，湍流扩散作用使颗粒在近壁面富集，而热泳力是PM2.5在冷壁面上发生沉积的最主要因素。得到了PM2.5热泳沉积的半经验公式，计算值与实验结果较为接近。

关键词: 可吸入颗粒物, 热泳力, 沉积效率